Miniaturization of a metal oxide semiconductor (MOS) type solid state image pickup device is progressing. For example, an average pitch between photodiodes as pixels is not longer than 1.4 μm. As a photodiode is made fine, a read transistor for reading an amount of signal charges converted by the photodiode is also made fine. As an area of a photodiode is reduced, a sensitivity lowers. As read transistors become small in size, their characteristics are varied.
Techniques are desired which efficiently dispose a photodiode, a read transistor and the like in a limited area. For example, a pixel unit structure has been proposed in which three photodiodes are disposed at three apexes of a triangle, and a floating diffusion to which signal charges converted by the photodiodes are transferred, a read transistor and the like are disposed near in a central area of the triangle (refer to JP-A-2006-165567).